1. Field of the Invention
The present invention relates to a quartz glass burner.
2. Description of the Related Art
Quartz glass burners are known which have a plurality of small diameter nozzles that are made up of relatively small diameter inner tubes and eject combustion assisting gas such as oxygen gas, and a large diameter nozzle that are made up of relatively large diameter tube enclosing these small diameter nozzles and ejects combustion gas such as hydrogen gas. The quartz glass burner is used for various flame workings by flowing combustion assisting gas through the small diameter nozzles and combustion gas through the large diameter nozzle enclosing the small diameter nozzles to burn them. Also, such quartz glass burner is used for depositing glass particles onto a porous glass preform by flowing glass raw gas through a central tube placed at the center of the burner, combustion assisting gas through small diameter nozzles, and combustion gas through a large diameter nozzle to produce the glass particles by flame hydrolysis reaction.
Conventionally, various researches have been focused on the number and arrangement of nozzles for flowing combustion assisting gas in such type of quartz glass burners in order to improve heating power on flame working or deposition efficiency on depositing glass particles on a porous glass preform. The Japanese Patent Laid-Open No. 2003-206154 defines the arrangement and number of nozzles, and the Japanese Patent Laid-Open No. 2003-165737 defines the diameter and linear velocity thereof. However, for improving the efficiency of flame working and deposition, it is important to consider not only the optimization of combustion assisting gas supplied from nozzles but the adjustment of combustion gas supplied from the large diameter nozzle.
One or more rows of small diameter nozzles are concentrically arranged within an outer tube. Typically, combustion gas ejection from small diameter nozzles in the row at the outermost circumference spreads out into surrounding atmosphere and burns without reacting with combustion assisting gas. Therefore, the wider area into which combustion gas is ejected outside the small diameter nozzles in the row at the outermost circumference gives the lower rate of combustion gas contributing to the heating of objects and the lower heating efficiency.
Furthermore, the increase in the number of small diameter nozzles to enhance heating power leads to the enlargement of a large diameter nozzle enclosing them. Thus, the enlargement of the diameter of combustion gas ejecting ports causes the further enlargement of the outside flow area from small diameter nozzles in the row at the outermost circumference to the outer tube, leading to the decrease in the rate of combustion gas contributing effectively to the heating of the objects. Therefore, the increase in combustion gas must be larger than that in combustion assisting gas so as to enhance heating power.